No brakes and master cylinder cap removal help

[Lisa P]

  Went to drive the '48 over to the other side of the shop last night and discovered that I had no brakes.  It appears to have a small leak from the passenger side rear wheel cylinder where I didn't tighten the brake line fitting well enough.  I tightened it and was prepared to add fluid and bleed the system, but could not get the cap off the master cylinder.  I have a large socket that fits it but cannot get in there to remove it.  What do you all do??  The master cylinder is new so it shouldn't be stuck, yet...  

[kaiserfrazerlibrary]

First thing (naturally enough) is wether or not you have a small socket extender that will raise the handle of the socket wrench enough to keep it above the floor board so  you can get leverage.  Second, if your master cylinder is cast iron you may want to spray some good penetrating oil (or marvel mystery oil) around the bottom of the cap.  This needs to be done carefully and you need to wipe off any excess to keep it from falling into the tank when the cap comes off.    This is what I did over the years with the various K-F products I owned to get the cap off in order to add fluid. 

You may also want to take the cap off once a month or so just to keep it from seizing up again.

[Fid]

The master cylinder was filled on Edgar's J in 2005. I got the car here in 2007 and had to replace the brake light switch in 2008. When I replaced that switch we lost some fluid and I had to fill it. That cap was stuck so tight I had to pound on it with a pry bar and a large hammer to knock it loose - I could not believe how tight it had siezed after just 3 years.  I replaced it with a plastic cap which I put a very thin layer of wheel bearing grease in the threads and made sure that none of it would get into the cylinder. We did this on  my '53 J back in the 70s and I have never had a problem getting the cap off it since.  As far as how to get yours off - I think the early cars have the master cylinder on the firewall, under the hood if I remember right.  Penetrating oil would be the first thing to try, then when you do get it off, lubricate the threads as suggested by kaiserfrazerlibrary and myself and you should be OK from then on.

[Lisa P]

Thanks for the responses guys!  I have socket extenders, penetrating oil and anti-seize.  I will tackle it tomorrow when there is more light and fewer mice.  A plastic cap sounds like a great idea-the master cylinder appears to be cast, the cap is brass maybe?  It is located waaaaay down on the frame.  I'll let you know how I make out, thanks again!